scholarly journals Apical Membrane Permeability of Mytilus Gill: Influence of Ultrastructure, Salinity and Competitive Inhibitors on Amino Acid Fluxes

1987 ◽  
Vol 129 (1) ◽  
pp. 205-230
Author(s):  
STEPHEN H. WRIGHT ◽  
TIMOTHY W. SECOMB ◽  
TIMOTHY J. BRADLEY
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Apical Membrane ◽  
Sea Water ◽  
Gill Tissue ◽  
Permeability Barrier ◽  
Acid Uptake ◽  
Passive Permeability ◽  
Membrane Area ◽  
Kinetics Of

The apical membrane of gill integumental cells from the mussels Mytilus edulis and M. californianus serves as a permeability barrier separating sea water from a cytoplasm rich in amino acids and other small organic molecules. Morphometric analysis of transmission electronmicrographs indicates that the membrane area of these cells is increased between 10- and 18-fold by the presence of a microvillous brush border. The microvilli do not appear to influence the kinetics of solute transport across the cell apex, as determined using a mathematical model of the relationship between membrane structure and the kinetics of transport. Rates of amino acid loss from the integument were low, and estimates of the upper limit of the passive permeability of the apical membrane to amino acids ranged from 0.5 to 10×10−10cm s−1. Abrupt exposure of intact mussels or isolated gill tissue to 60% sea water (19% salinity) resulted in a transient, 40- to 80-fold increase in the rate of loss of all amino acids from integumental tissues. Upon exposure to full-strength sea water, efflux rates returned to near control values. Exposure to 60% sea water also inhibited the carrier-mediated accumulation of amino acid: uptake of 0.5 μmol1−1 [14C]alanine and [14C]taurine was reduced by 80% compared to control uptake in 100% sea water. This inhibition was not adequate to account for the increase in net efflux of taurine from gill tissue into 60% artificial sea water (ASW), though the inhibition of alanine uptake may have contributed significantly to the increased loss of this amino acid. Efflux of discrete structural classes of amino acid occurred when integumental tissues were exposed to 50 μmoll−1 concentrations of structurally related analogues. It is concluded that the apical membrane of gill cells has a very low passive permeability to amino acids, and that the overall permeability of the gill can be increased in a reversible fashion by exposure to reduced salinity or to high external concentrations of amino acid.

scholarly journals Dicarboxylic Amino Acid Uptake in Normal, Friedreich's Ataxia, and Dicarboxylic Aminoaciduria Fibroblasts

1979 ◽  
Vol 6 (2) ◽  
pp. 263-273 ◽  
Author(s):  
S.B. Melancon ◽  
B. Grenier ◽  
L. Dallaire ◽  
M. Potier ◽  
G. Fontaine ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Uptake ◽  
Friedreich’S Ataxia ◽  
Friedreich's Ataxia ◽  
Acid Uptake ◽  
Normal Cells ◽  
Dicarboxylic Amino Acid ◽  
Normal Individuals ◽  
Kinetics Of

SummaryGlutamic and aspartic acid uptake was measured in skin fibroblasts from patients with Friedreich's Ataxia, dicarboxylic aminoaciduria, and normal individuals. The results showed no difference in uptake kinetics of either dicarboxylic amino acids between Friedreich's Ataxia and normal cells, but reduced uptake velocities in dicarboxylic aminoaciduria fibroblasts. Friedreich's Ataxia fibroblasts were, however, less calcium-dependant and more magnesium and phosphate-dependent than controls in glucose-free incubation mixture. This difference might be related to some degree of glucose intolerance by Friedreich's Ataxia fibroblasts in culture.

Influence of organic cations on basic amino-acid uptake by human placental villi

1995 ◽  
Vol 7 (6) ◽  
pp. 1491
Author(s):  
RB Krishna ◽  
J Dancis ◽  
M Levitz
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Basic Amino Acid ◽  
Amino Acid Uptake ◽  
Progressive Increase ◽  
Amino Acid Transporters ◽  
Acid Uptake ◽  
Chorionic Villi ◽  
Basic Amino Acids ◽  
Kinetics Of

Human placental chorionic villi were incubated for 30 min with [3H]lysine or [3H]arginine and the distribution ratios (intracellular:extracellular concentrations) were determined. The ratios remained unchanged when Na+ in Earle's buffered salt solution was replaced with Li+. When Na+ was replaced with choline there was a significant increase is distribution ratios (lysine 1.34 +/- 0.33 v. 3.99 +/- 0.15, arginine 1.95 +/- 0.37 v. 5.05 +/- 1.16). Leucine, a neutral amino acid with a Na(+)-independent transport system, was unaffected by choline substitution. The distribution ratio for alanine, which is Na(+)-dependent, was reduced (2.50 +/- 0.41 v. 1.45 +/- 0.20). Two other quarternary amines, acetyl-beta-methylcholine and tetraethylammonium chloride (TEA) caused similar increases in the distribution ratios of the basic amino acids. Hordenine, a tertiary amine, was less effective and there was little or no effect with ephedrine, a secondary amine. The choline effect was first observable at concentrations of 105 mM. With TEA, there was a progressive increase in distribution ratios beginning at 29 mM. Lysine efflux was measured after incubation of villi with lysine in Earle's buffer or choline buffer. Lysine was rapidly released to the fresh medium with 25% more retained in choline-exposed villi. The amines may cause alterations in the kinetics of basic amino-acid transporters or may modify other aspects of placental physiology permitting an increase retention of the basic amino acids.

Trans-tegumental absorption of L-alanine and L-leucine by a monogenean, Diclidophora merlangi

Parasitology ◽  
1978 ◽  
Vol 76 (1) ◽  
pp. 29-37 ◽  
Author(s):  
D. W. Halton
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Amino Acid ◽  
Sea Water ◽  
Low Molecular Weight ◽  
Acid Uptake ◽  
Neutral Amino Acids ◽  
Freeze Dried ◽  
Significant Difference

SummaryAn in vitro investigation has been made of the relative roles of the gut and tegument in the absorption of the neutral amino acids L-alanine and L-leucine by a marine fish-gill parasite, Diclidophora merlangi. The use of ligatures to preclude oral ingestion of trace-labelled medium has proved inadequate, invariably damaging the tegument, as revealed by stereoscan electron microscopy, and resulting in artifactual levels of absorption. Three alternative procedures have given consistently reliable data on the route of entry of low molecular weight substrates. (1) Ultrastructural examination of worms previously incubated in electron-dense cationic tracers has shown that, in vitro, there is no oral intake of sea water. (2) The suspending of worms in trace-labelled medium with the mouth out of the medium and comparing amino acid uptake with that of worms totally immersed in medium has revealed no statistically significant difference in the absorption levels. (3) Application of section (freeze-dried) auto-radiography to detect diffusible isotope has demonstrated directly transtegumental absorption of a neutral amino acid. It is concluded from these experiments that Diclidophora has a tegumental transport system for absorbing certain neutral amino acids, and whilst, clearly, the worm is sanguinivorous and digests blood in a well-developed gut, it may also be capable of supplementing this diet with low molecular weight organic nutrient absorbed directly from sea water via the tegument.

scholarly journals Intracellular Na+ and the control of amino acid fluxes in the integumental epithelium of a marine bivalve

1989 ◽  
Vol 142 (1) ◽  
pp. 293-310
Author(s):  
S. H. Wright ◽  
D. A. Moon ◽  
A. L. Silva
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Sea Water ◽  
Gill Tissue ◽  
Transport Systems ◽  
Amino Acid Transporters ◽  
Marine Bivalve ◽  
Chemical Gradients ◽  
Influx Pathways ◽  
Taurine Efflux

The accumulation of amino acids from sea water into the integumental epithelium of the bivalve gill can occur against chemical gradients in excess of 10(6) to 1. The energy to drive this transport has been proposed to come from the inwardly directed Na+ electrochemical gradient. The present study examined the influence of intracellular and extracellular [Na+] on influx and efflux of amino acids in gill tissue from the mussel, Mytilus californianus. Influx of alanine was inhibited by more than 90% when external [Na+] was reduced from 425 to 2 mmol l-1, and by 85% when intracellular [Na+] was increased from approximately 11 to approximately 100 mmol l-1 (by means of a 30-min exposure to the ionophore, nigericin). Efflux of taurine and alanine from gill tissue into normal-Na+ sea water was very low (less than 5% of the Jmax of the carrier-mediated influx pathways). Reducing the external Na+ from 425 to 2 mmol l-1 increased taurine efflux by only 20%. Raising cell [Na+] to approximately 100 mmol l-1 increased taurine efflux 2.7-fold; further increases in cell [Na+] increased taurine efflux another 7.5-fold. These data, in conjunction with results from earlier studies, suggest that activation of integumental amino acid transporters requires an interaction of multiple sodium ions with binding sites of low affinity for this ion. This set of characteristics results in transport systems that are well-adapted for the net accumulation of amino acids from sea water.

Kinetics of Uptake of An Amino Acid and a Dipeptide into Hamster Jejunum and Ileum: The Effect of Semistarvation and Starvation

1979 ◽  
Vol 56 (5) ◽  
pp. 487-492 ◽  
Author(s):  
H. P. Schedl ◽  
D. Burston ◽  
Elizabeth Taylor ◽  
D. M. Matthews
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Unit Length ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Intestinal Uptake ◽  
Main Effect ◽  
Kinetics Of Uptake ◽  
Kinetics Of

1. This paper reports an investigation of the effects of semistarvation and starvation on the kinetics of uptake of an amino acid, l-leucine, and a hydrolysis-resistant dipeptide, Gly-Sar, by rings of everted hamster jejunum and ileum in vitro. The concentration range used was 0·1–100 mmol/l. Total uptake, non-mediated uptake and Kt and Vmax. for mediated influx were estimated. 2. At many concentrations, both semistarvation and starvation caused a decrease in uptake of the peptide and the amino acid. Uptake of the peptide was more severely depressed than that of the amino acid. In control animals, the jejunum was the site of maximal uptake of Gly-Sar, and the ileum the site of maximal uptake of leucine. In semistarved and starved animals, the ileum became the site of maximal uptake of Gly-Sar, as it was for leucine. The effects of semistarvation and starvation on uptake were similar whether this was expressed per unit wt. or per unit length, though they were accentuated when expressed per unit length, since the intestine lost weight per unit length. 3. The main effect of semistarvation and starvation on the kinetics of mediated influx of the amino acid and the peptide was to reduce Vmax. in both jejunum and ileum. This effect was compatible with a reduction in the number of mediated transport sites for both the amino acid and the peptide. The observation that mediated influx of the peptide was more severely affected than that of the amino acid supports the hypothesis of the independence of the mechanisms for intestinal uptake of peptides and amino acids.

Gamma-Glutamyl-Amino Acids as Signals for the Hormonal Regulation of Amino Acid Uptake by the Mammary Gland of the Lactating Rat

Neonatology ◽  
1985 ◽  
Vol 48 (4) ◽  
pp. 250-256 ◽  
Author(s):  
Juan R. Viña ◽  
Inmaculada R. Puertes ◽  
Juan B. Montoro ◽  
Guillermo T. Saez ◽  
José Viña
Keyword(s):  
Amino Acids ◽  
Mammary Gland ◽  
Amino Acid ◽  
Hormonal Regulation ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Gamma Glutamyl

SOME ASPECTS OF THE STRUCTURE OF HEMOGLOBIN

1964 ◽  
Vol 42 (6) ◽  
pp. 755-762 ◽  
Author(s):  
David B. Smith
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Partial Amino Acid Sequence ◽  
Heme Pocket ◽  
Terminal Amino ◽  
Polypeptide Chains ◽  
Kinetics Of ◽  
Β Chain

An outline of present ideas concerning the arrangement, folding, and chemistry of the polypeptide chains of hemoglobin is given with some references to present know ledge of myoglobin.New material includes a partial amino acid sequence of the β-chain of horse hemoglobin, details concerning the amino acids lining the heme pocket of horse hemoglobin, and the effects of carboxypeptidases A and B on horse oxy- and horse deoxy-hemoglobin. The kinetics of the latter reactions are not simple. The C-terminal amino acids are released more rapidly from the oxygenated form.

scholarly journals Identification in skeletal muscle of a distinct extracellular pool of amino acids, and its role in protein synthesis

1971 ◽  
Vol 121 (5) ◽  
pp. 817-827 ◽  
Author(s):  
R. C. Hider ◽  
E. B. Fern ◽  
D. R. London
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Incubation Medium ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Longus Muscle ◽  
Kinetics Of

1. The kinetics of radioactive labelling of extra- and intra-cellular amino acid pools and protein of the extensor digitorum longus muscle were studied after incubations with radioactive amino acids in vitro. 2. The results indicated that an extracellular pool could be defined, the contents of which were different from those of the incubation medium. 3. It was concluded that amino acids from the extracellular pool, as defined in this study, were incorporated directly into protein.

scholarly journals Action of growth hormone in vitro on the net uptake and incorporation into protein of amino acids in muscle from intact rabbits given protein-deficient diets

1976 ◽  
Vol 35 (1) ◽  
pp. 1-10 ◽  
Author(s):  
M. R. Turner ◽  
P. J. Reeds ◽  
K. A. Munday
Keyword(s):  
Amino Acids ◽  
Growth Hormone ◽  
Protein Synthesis ◽  
Amino Acid ◽  
De Novo ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Amino Acid Incorporation ◽  
Acid Incorporation

1. Net amino acid uptake, and incorporation into protein have been measured in vitro in the presence and absence of porcine growth hormone (GH) in muscle from intact rabbits fed for 5 d on low-protein (LP), protein-free (PF) or control diets.2. In muscle from control and LP animals GH had no effect on the net amino acid uptake but stimulated amino acid incorporation into protein, although this response was less in LP animals than in control animals.3. In muscle from PF animals, GH stimulated both amino acid incorporation into protein and the net amino acid uptake, a type of response which also occurs in hypophysectomized animals. The magnitude of the effect of GH on the incorporation of amino acids into protein was reduced in muscle from PF animals.4. The effect of GH on the net amino acid uptake in PF animals was completely blocked by cycloheximide; the uptake effect of GH in these animals was dependent therefore on de novo protein synthesis.5. It is proposed that in the adult the role of growth hormone in protein metabolism is to sustain cellular protein synthesis when there is a decrease in the level of substrate amino acids, similar to that which occurs during a short-term fast or when the dietary protein intake is inadequate.

The uptake of amino acids by mouse cells (strain LS) during growth in batch culture and chemostat culture: the influence of cell growth rate

1967 ◽  
Vol 168 (1013) ◽  
pp. 421-438 ◽  
Keyword(s):  
Amino Acids ◽  
Growth Rate ◽  
Amino Acid ◽  
Cell Growth ◽  
Glutamic Acid ◽  
Batch Culture ◽  
Amino Acid Uptake ◽  
Essential Amino Acids ◽  
Growth Yields ◽  
Acid Uptake

The uptake of thirteen essential amino acids by mouse LS cells in suspension culture was determined by bacteriological assay methods. Chemostat continuous-flow cultures were used to determine the effect of different cell growth rates on the quantitative amino acid requirements for growth. The growth yields of the cells ( Y = g cell dry weight produced/g amino acid utilized) were calculated for each of the essential amino acids. A mixture of the non-essential amino acids, serine, alanine and glycine increased the cell yield from the essential amino acids. The growth yields from nearly all the essential amino acids in batch culture were increased when glutamic acid was substituted for the glutamine in the medium. The growth yields from the amino acids in batch culture were much less at the beginning than at the end of the culture. The highest efficiencies of conversion of amino acids to cell material were obtained by chemostat culture. When glutamic acid largely replaced the glutamine in the medium the conversion of amino acid nitrogen to cell nitrogen was 100 % efficient (that is, the theoretical yield was obtained) at the optimum growth rate (cell doubling time, 43 h). The maximum population density a given amino acid mixture will support can be calculated from the data. It is concluded that in several routinely used tissue culture media the cell growth is limited by the amino acid supply. In batch culture glutamine was wasted by (1) its spontaneous decomposition to pyrrolidone carboxylic acid and ammonia, and (2) its enzymic breakdown to glutamic acid and ammonia, but also glutamine was used less efficiently than glutamic acid. Study of the influence of cell growth rate on amino acid uptake rates per unit mass of cells indicated that a marked change in amino acid metabolism occurred at a specific growth rate of 0.4 day -1 (cell doubling time, 43 h). With decrease in specific growth rate below 0.4 day -1 there was a marked stimulation of amino acid uptake rate per cell and essential amino acids were consumed increasingly for functions other than synthesis of cell material.

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